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Help with Luxman R-1050

K

Kadosas

New Member
Hello,

I am working on a Luxman R-1050. I had it in a working condition, the only thing was that i measured a DC offset voltage of about 20 mV and therefor I replaced the 2 SA750 (Q101 and Q102) with perfectly matched KSA992FBU's in both chanels. While I was at it I also replaced the input capacitors (3,3 uF, C101a + C101b)) electrolytes for a poly propylen type.
I powered it one and everything was alright. I had about 20mA on both my multimeters. The multimeters were connected there where the fuses 102a and 102b normally are. The service manual says that the idle current should be 50 mA, so I adjusted the trimmers. But while doing that, after about 25 mA the current suddenly shoots up to more than 140mA with the result of some very hot transistors ;-) . In other words I am not "allowed" to turn it up to 50 mA.

What could that be? Was it wrong to replace the electrolyt with a poly propelyn? Is it some feedback isue?

Help would be appreciated.
 
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Sure, I tell you. It had something to do with the powertransistors. When I measured for continuity on the powertransistors (the collector) themself I knew I should have continuity between the collectors of both channels, in other words between the D388A from the left and right channel and between both B541A from the right and left channel. If you look at the schematic you can see they are connected with each other (there is no connection between D388A and B541A). Anyway, it turned out that those small plastic round things (I don't no the name of them) you put on the powertransistor to keep it in place, they were isolating the screws from the housing of the powertransistors and thus there was no continuity. After I removed them there was no problem anymore and I could adjust the current to 50mA without a problem.

I hope it makes sense!?
 
Your very welcome. Now I can close my R-1050 and continue with my R-1070. I did this "triac-thing" with the powerswitch, and it works like a dream...BUT, now I can hear that the transformator makes a little sound like "rrrrrrrrrrrrrrrr", and I can feel a slight trembling when I touch it.
Hmmm. I wonder, could it be the Triac? Maybe because its switching all the time?

So, that is my next challenge.
 
I have a relay to install in an R-1120 so hoping to avoid the "rrrrrrr". Maybe you can add to the triac thread to see what folks think.
 
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